Question

这件事情很好：

SELECT c.id, c.name, c.ascii_name, COUNT(*) AS nr
    FROM cities c 
    INNER JOIN jobs j ON (j.city_id = c.id ) 
    WHERE j.is_active = 1 
    GROUP BY c.name
limit 100

但是，当我想把条件放在新列上时，它表示列未找到

SELECT c.id, c.name, c.ascii_name, COUNT(*) AS nr
    FROM cities c 
    INNER JOIN jobs j ON (j.city_id = c.id ) 
    WHERE j.is_active = 1 and nr > 100
    GROUP BY c.name
limit 100

Answer 1

您应该在HAVING子句中将条件放在nr上，如下所示：

SELECT c.id, c.name, c.ascii_name, COUNT(*) AS nr
    FROM cities c 
    INNER JOIN jobs j ON (j.city_id = c.id ) 
    WHERE j.is_active = 1
    GROUP BY c.name
    HAVING nr > 100
limit 100

这是因为nr是聚合函数（COUNT（*））的结果，因此在应用WHERE过滤器时不可用。

编辑：在某些数据库服务器中，对nr的引用不起作用;您也可以使用HAVING COUNT(*) > 100。

Answer 2

你应该把你的陈述读成

SELECT c.id, c.name, c.ascii_name, COUNT(*) AS nr
             FROM cities c 
             INNER JOIN jobs j ON (j.city_id = c.id ) 
             WHERE j.is_active = 1
             GROUP BY c.name
HAVING COUNT(*) > 100
limit 100

Answer 3

SELECT c.id，c.name，c.ascii_name，COUNT（*）AS nr 来自城市c INNER JOIN作业j ON（j.city_id = c.id） WHERE j.is_active = 1和nr.c.id＆gt; 100 GROUP BY c.name 限制100

SQL：将条件置于聚合函数的结果上

3 个答案: